An eco-friendly system of thermally regenerative battery-driven electrochemical CO2 reduction: In-situ harvesting of low-grade heat as electrical power for reducing CO2 emissions of flue gas

Abstract

To realize the utilization of power energy from thermally regenerative batteries and treat flue gas, an eco-friendly coupled system of thermally regenerative battery-driven electrochemical reduction of carbon dioxide is proposed. This system recovers low-grade waste heat for electrical power while in-situ utilization for carbon dioxide reduction. The results show that carbon nanotubes-loaded silver catalyst enhances electrochemical carbon dioxide reduction performance due to increased active sites exposure. Output voltage and maximum power correlate linearly with the number of cell pairs in the thermally regenerative battery stack. Operating with 4 cell pairs, the eco-friendly coupled system achieves an average carbon monoxide Faradaic efficiency of 76.6 % and an average carbon monoxide Faradaic current density of 5.4 mA cm⁻². A minimum of 3 cell pairs is necessary for system operation. The increase of cell pairs in a certain range is beneficial for the performance improvement of electrochemical reduction of carbon dioxide. The eco-friendly coupled system attains an average Faradaic efficiency of 89.4 % and an average carbon monoxide Faradaic current density of 17.8 mA cm⁻² with 8 cell pairs. This coupled system indicates a feasible and promising way to simultaneously reduce the emission of low-grade waste heat and carbon dioxide in flue gas without additional inputs.